1. Field of the Invention
This invention relates to an automatic selection system of two electronic circuits, a primary unit and a standby unit, initiated by a malfunction-alarming signal from one of them.
2. Description of the Related Arts
In a prior art switching system between its primary circuit and standby circuit, a control circuit is provided independently from the two circuits so as to transmit a switching instruction to both of the circuits upon receiving an alarm signal generated by one of the circuits. Recently in the control circuit a small data processor called a micro processor unit (MPU) is preferably employed to judge the alarm signal and then transmit the switching instruction to the two circuits.
In the prior art control circuit employing MPU is advantageous in that the conditions in judging the alarm and in the switching instruction can be easily modified by the program set in the MPU. However, there is a problem in that the MPU collecting various data takes them a considerably long time, for example 50 ms, to process them. Accordingly, the delay in switching the circuits causes loss of the data or discontinuation of clock signals.